Electric power converting apparatus



March 21, 1933. I s, rrz GERALD 1,902,495"

ELECTRIC POWER couvmmue APPARATUS Filed Aug. 8, 1930 Im/entor: Alan S. FLtz Gerald.

l-lLs Attorne g.

Patented Mar. '21, 1933 I -UNITED STATES PATENT OFFICE ALAN S. FITZ GERALD, OF WYNNEWOOD, PENNSYLVANIA, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC POWER CONVERTING APPARATUS Application-filed August 8, 1930; Serial No. 473,913.

My invention relates to electric power conalternating current system 12, through two verting apparatus and more particularly to parallel circuits. The first of these circuits converting apparatus for transmitting power includes an electric discharge device 16, a cafrom a direct current source of supply to an pacitor 14,the primary winding 15 of a transalternatin curr nt y t former l3 and an electric discharge device 17.

Th present i ti tit t n im- The other parallel circuit includes an electric provement on that forming the subject matdischarge device 18, the primary winding ter of United States Letters Patent No. 1,752,- of the transform r 1 t e capacitor 1 a d 7 I247, granted March 1930, upon my applian e e t c discharge device 19. Each of the 0 cation and assigned to the same assignee as electric discharge devices 16 to 19 includes '60 the present application. In this earlier patthe usual cathode and anode and controlling cut I have disclosed a simple and economical grids 22 to 25 1n0lusive. These grids are conpower converting apparatus in which a canected t0 theli I'BSPQCUVQ cathodes through pacitor is connected in series with the load h ng b ries 26 and the secondary wind- 15 circuit and the charging and dischargi lugs 27 to 9 0, respectively of a transformer '65 currents of the capacitor are transmitted he pr mary Wlndlng of transformer through different electrical discharge valves 3 1S pp W h e n tlllg c rrent of a to the alternating current system. a The ap frequency the same as that, d r d o th paratus d ib d i th t t t h alternating current system 12. A reactor 20 has the disadvantage that power is drawn may be Inserted between the discharge defrom the direct current supply only during 7 vlces 1 and 1 and aslmilar to 21 y alt t h lfl l f th power t t, be inserted between the discharge devices 16 with the result that the direct current system and P RO a fi Set forth. i t t d t it maximum it The circuit including the capacitor 14 and 25 angbject fny invention to provide the primary winding Of the'transformer iso nating current circuit.

improved electric, power converting appa- IS connected between the Of these ratus which will eiiectively provide for the FeaCtOrS- v a r transfer of a maximum amount of energy be- The eleCtPIC l h rg devices 16 to 19 may tween a direct current circuit and an alterhe of a y O the yp s W811 OWH in the art,

. A such for example, as the vapor electric type '30 Acc rding t my r t, i v ti I v rin which the current between the cathode come the disadvantage of my prior arrangen l an demay be prevented from starting ment by providing a double-acting circuit by l P 1g the proper potential upon the including four electric discharge valves. In cont-rolllng g d in Which the e v535 this arrangement the capacitor issuccessivee L t g by impressing a more p0si ly charged to opposite polarities so that powtiVe P II i I upon he gTi 01" the pure er is drawn continuously from the direct curelectron thermionic emission type in which rent supply during each of the charging cythe current between the cathode and anode cles. V v- 7 V is continuously controlled by the gridpoten- 40, My invention will. be better understood tial. from the following description taken in con- Assuming that a direct current potential nection with the accompanying drawing and is impressed across the leads 10 and 11 and its scope will be pointed out in the appended the potential derived from the secondary claims. winding 27 is of such magnitude and of the In the accompanying drawing 1 have diright polarity to overcome the grid bias of 5 agram'matically illustrated my invention as the battery 26 so thatthe discharge device applied to asynchronously driven inverter. 16 is made conducting, the same potential Referring to the drawing I have shown a will simultaneously be impressed upon the source of direct current supply comprising grid of the discharge device 17 and a cur- 0 the leads'lO'and 11 interconnected with an rent will flow-through the discharge device. v

case the pure electron discharge type is em- 7 ployed. Immediately thereafter the polarity of the grid potentials is reversed, the discharge devices 16 and 17 made non-conducting and the dischargedevices 18 and 19made conducting. Inthis condition, the potential across the capacitor 1a is cumulative with.

that of the direct current supply and a current will flowfrom conductor lO through discharge device 18, winding 15, capacitor 1 1 and discharge device 19 to the other side of the line, until the capacitor 14 is completely charged to the oppositepolarity or untilthe devices 18 and19 are made non-conducting. Itis obvious that this cycle will be repeat ed at a'frequency depending upon tne alter nating current potential supplied to the T transformer 31. In the successive changes in the current flow-between the two parallel paths it isnoted that the current fiowsin opposite directions through the winding with I the result that analternating current is sup- ,7 plied'to the lines12."

In the above description-it has been assumed that the discharge devices 16 to '19 were of the pure electron discharge type in V which the current flow is under the complete controlofthe grids. If these devices are of the vapor dischargetype in which the grids control only the starting of the current through the device, it is necessary to include either the reactor 20 01 21 or preferably both. In case the devices 18 and 19 should be made conducting before the current has been interrupted inthe parallel circuit, whiclris the case when the driving frequency of the transformer 32 is above the natural frequen cy 'of thesystem,,there Would be a virtual 9 tervoltage is'inducedfin the other portions of short circuit'acrossthe lines-1O and 11. By

'pro vidinglthe'reactors'20 and 21, however, as soon as the current begins to flow through thedischarge devices 18 and 19, through the righthand portion ofthe reactor 20, and the left hand portion of the reactor 21, a counthese reactors which is in opposition to-the voltagebetween the anodes and cathodes of th'ejdisch'ar'ge devices 16 and17 and greater 'ininagnitude, with the result that the cur" rent in these devices is quickly interrupted. 'While I have shown and described what I at present consider the preferred embodiinent of my invention, it 'will be obvious to those skilled'in the art that changes and -1nodifications' maybe made without depart ingffrom my invention and-I therefore aim in the appendedclaims to 'cover"al l such changes andmodificationsas fall within the true'spirlt andscope of my invent on.

whatlclann as new; and deslre to secure 1. In a system for converting direct ouring current, th-ecombination of a source of direct current, a plurality of electrical valves, a capacitor, a circuit including a plurality of said valves for charging said capacitor from the full voltage of said source, a circuit including a plurality of other of said valves for oppositely-charging said capacitor from the full voltage of said source, means for controlling the conductivities of said valves,'and an output circuit common to both of said charging circuits and adapted to furnish periodically varying currents.

2. In a system for converting direct current electrical energy into periodically varying current, the combination ofa source of direct current, a plurality of electrical valves,

full'voltage of said source, a circuit i'nclud-' .rent electrical energy into periodically varying another pair of said valves for 'oppo-' V sitely charging said capacitor from the full voltage of said source, an output circuit com T monto both of said charging clrcults and adaptedto furnish periodically varying currents, and-means for successively changing the conductivities of saidpairs of valves.

' 3. The combination ofa sourceof direct current, a plurality of vapor electric-discharge devices, each. provided with a grid for controlling the startingof current between-its catl1'ode'and anode,a capacitor, a circuit including a'pair of said discharge devices for chargingsaid capacitor from the full voltage of said source, a circuit including another pair of said discharge devices foreppositely charging said'capacitor from thelfull voltage of said source, an alternating current circuitcominon to both of said charging circuits, and means for" controlling the potenttials of said grids;

current, a plurality ofvapor electric discharge devices eachrprovided with agrid for controlling the'startingiof current-between its a cathode and anode,a.capacitor; a circuit/including a'pair of said discharge devices for charging said capacitorfrom'the full voltage of said source, ;a 'circnit including-anotherpair of said discharge'devices for opcircuits, and means" for applying 7 alternating 4. The. combination of afsource of direct 7110 potentials ofopposed-polaritiesfto the grids of said pairs of discharge devices.

5. Inca system for converting directcurrent electricalenergy into alternating current, the combination of a sourceofdirect current, a plurality OfGlGCtIYlCYLlVGS, a capac- 1tor,'a c1rcu1t nclud ng a palrof saidvalves and said capacitor connected serially-across -sa1dsource,"a second circuit including another pair of said valves and said capacitor connected serially and in parallel to said first circuit, means for controlling the conductivities of said valves, and an alternating 5 current output circuit common to both of said first mentioned circuits.

6. In a system for converting direct current electrical energy into alternating current, thecombination of a source of direct current, a

plurality of electric valves, a capacitor, two

parallel circuits connected across said source, each circuit including a difi'erent pair of said valves, said capacitor being connected between the valves of both circuits, means for successively and alternately rendering the pairs of valves conducting and non-conducting, and an alternating current output circuit common to both of said first-mentioned circuits.

In Witness whereof, I have hereunto set my hand this 6th day of August, 1930.

ALAN S. FITZ GERALD. 

